Numerous devices have been devised over the years for measuring the angular or linear displacement of an object. One such device, known as an inclinometer, measures the inclination of an object relative to one or more horizontal axes. For example, an inclinometer that is able to measure the angular orientation or inclination of a ship or a boat may consist of a curved tube filled with a liquid containing a bubble. The tube is aligned abeam and attached to a vertical structure on the center line of the vessel. As the vessel tilts or inclines off the vertical, the bubble aligns with a number on a scale running the length of the tube, thereby indicating the degree of the vessel's tilt. Data generated by such devices, however, cannot be readily converted into electronic form.
Another known device for measuring displacement is based on the extent of motion of a sensor across a variable resistor. The amount of current flowing through the resistor following displacement is compared to a base value, thereby to determine the amount of angular or linear displacement. This type of measurement device, however, requires the use of an analog-to-digital converter to display this measurement in digital form or for further digital data processing.
Yet a further known displacement-measuring device employs a light source, typically a laser, to read codes imprinted on an object that rotates or otherwise moves in response to the force that is causing the displacement. The codes are positioned such that the amount of the displacement causes the code that indicates that amount to become aligned with the beam of light that reads the code, thereby to produce a digital signal that represents the measured displacement.
Devices are also known for measuring the inclination of an object that measure the magnitude of inclination and produce an electrical analog or digital signal that is representative of the inclination angle. For example, in U.S. Pat. No. 6,449,857 there is shown an electronic inclinometer in which measuring electrodes are located on the exterior of a dielectric cell that is isolated from a sensor fluid. The signals derived by the sensors are converted to frequency signals that are processed by a microprocessor. Other prior art electronic inclinometers are disclosed in U.S. Pat. Nos. 6,578,797; 6,249,984; 5,774,996; 5,761,818; 5,428,902; and 4,811,491.
Whereas the known prior art displacement-measuring devices, such as those described above, provide generally accurate measurements of angular or linear displacement, they each fall short in some manner of providing digital displacement measurement data in a relatively direct, simple and low-cost manner and with high reliability and low power consumption.